Nintendo has been pretty successful in the handheld gaming market with its Nintendo DS, but that could change once Apple opens the App Store for the iPhone and iPod touch for business. The ability to code games that take advantage of Apple’s motion sensors coupled with wireless application downloads may be more competition than Nintendo can handle, according to Forbes.

Apple plans to launch its App Store in June, which will give iPhone and iPod touch owners an easy way to buy and install third-party applications even when they are away from their computers. Developers have already been hard at work coding their apps for Apple’s handheld devices thanks to the early release of the iPhone software developer kit.

Many of those developers are likely working on games, and they will take advantage of the handheld’s true multi-touch interface and built-in motion sensors to create new game interfaces that go beyond the Nintento DS’s capabilities.

Electronic Arts and Sega, both big names in the gaming market, have already shown off early versions of iPhone games that looked just as polished as shipping products, and both companies bragged about how easy the coding was. More game developers have been announcing iPhone and iPod touch support over the past few months, which means there will likely be plenty to choose from when the App Store opens its doors, and more will likely follow.

That interest in mobile games could turn Apple’s iPhone and iPod touch into serious gaming platforms, and give Nintendo some new competition from an unlikely source.